Rare Earth-Rich Indides <Emphasis Type="Italic">RE</Emphasis><Subscript>5</Subscript>Pt<Subscript>2</Subscript>In<Subscript>4</Subscript> (<Emphasis Type="Italic">RE</Emphasis> = Sc,Y, La–Nd,Sm, Gd–Tm,Lu)

Summary. The isotypic indides RE ₅Pt₂In₄ (RE = Sc, Y, La–Nd, Sm, Gd–Tm, Lu) were synthesized by arc-melting of the elements and subsequent annealing. They were investigated via X-ray powder diffraction. Small single crystals of Gd₅Pt₂In₄ were grown via slow cooling and the structure was refined from X-ray single crystal diffractometer data: Pbam, a = 1819.2(9), b = 803.2(3), c = 367.6(2) pm, wR ² = 0.089, 893 F ² values and 36 parameters. The structure is an intergrowth variant of distorted trigonal and square prismatic slabs of compositions GdPt and GdIn. Together the platinum and indium atoms build up one-dimensional [Pt₂In₄] networks (292–333 pm Pt–In and 328–368 pm In–In) in an AA stacking sequence along the c axis. The gadolinium atoms fill distorted square and pentagonal prismatic cages between these networks with strong bonding to the platinum atoms.     

2D-QSAR Studies on Triazolone Compounds Containing Benzenesulfonic Amide

The geometry structures of 6 triazolone compounds containing benzenesulfonic amide were fully optimized with DFT (Density Functional Theory) method at the B3LYP/6-31G level, and the structural and electronic parameters of the compounds were calculated. The hydrophobic and topological parameters of the title compounds were calculated by HyperChem software. The mono-and bi-parametric models between the parameters and biological activity of the compounds were analyzed by Multiple Linear Regression method based on Hansch-Fujita model. The results show that the activities of the title compounds were increased with higher hydrophobic property logP and molecular volume V, lower molecular energy ETOTAL and elec-tronegative of benzene ring Qph.     

The challenge of achieving traditional exterior durability performance in low VOC architectural coatings

Over the years the optimization of water-borne emulsion polymers has resulted in water-borne coatings with excellent exterior durability and significantly reduced solvent emissions versus solvent-borne coatings. In recent years, pressure to further reduce emissions has necessitated the use of softer polymer compositions which can negatively impact gloss and tint retention, and dirt pick up resistance. The use of heterogeneous polymer morphologies are addressing these short comings; however care must still be taken not to affect paint durability. The development of low solvent emission thickeners and mildewcides has allowed further reduction in paint emissions.     

Silica supported perchloric acid (HClO4-SiO2): an efficient reagent for the preparation of primary carbamates under solvent-free conditions

The synthesis of primary carbamates from structurally diverse compounds containing a hydroxyl group has been performed in high yields and purity, and without any epimerization under solvent-free conditions using HClO₄-SiO₂ as a mild, convenient, and effective reagent. The procedure is operationally simple, efficient, and environmentally benign.     

A New Versatile and Sensitive Monitoring System for Liquid Chromatography: Cerate Oxidation and Fluorescence Measurement

Abstract

A new liquid chromatographic detector depends upon the fluorescence measurement of cerium (III) produced from the reaction of cerium (IV) with eluted reducible compounds. It is more sensitive than previous oxidative detectors by more than a factor of 100. The reaction can be varied to discriminate among compounds according to ease of oxidation.     

The concept of in-situ vapor stripping for removing VOCs from groundwater

An in-situ remediation procedure is proposed to remove Volatile Organic Compounds (VOCs) dissolved in groundwater. This is accomplished by injecton of air into a well, using a combined technique of air-lift pumping with a form of vapor stripping. When air is injected into a well, it causes water to be lifted and forces groundwater flow towards the well, creating a recirculating cleanup zone. During this process, VOCs are transferred from the contaminated water to the rising air bubbles inside the well. The air bubbles are separated from the liquid near the top of the well, and the VOC vapor is collected and treated. In this system, water is not permitted to be lifted to the ground surface. Rather, the water is diverted into the unsaturated zone through a series of drains that are installed beneath the root-zone. The water then, free of a portion of VOCs, infiltrates back to the water table. As water continues to circulate, the VOC concentrations are gradually reduced.The feasibility of the proposed method was analyzed using concepts of mass transfer of VOCs from water to air-bubbles. Calculations indicate that the method has promise because equilibrium partitioning between the contaminated liquid and the gas bubbles is rapidly established.     

Stereodivergent Synthesis of Allenes with α,β-Adjacent Central Chiralities Empowered by Synergistic Pd/Cu Catalysis

The stereodivergent synthesis of allene compounds bearing α,β-adjacent central chiralities has been realized via the Pd/Cu-catalyzed dynamic kinetic asymmetric alkylation of racemic allenylic esters. The matched reactivity of bimetallic catalytic system enables the challenging reaction of racemic aryl-substituted allenylic acetates with sterically crowded aldimine esters smoothly under mild reaction conditions. Various chiral non-natural amino acids bearing a terminal allenyl group are easily synthesized in high yields and with excellent diastereo- and enantioselectivities (up to >20 : 1 dr, >99 % ee). Importantly, all four stereoisomers of the product can be readily accessed by switching the configurations of the two chiral metal catalysts. Furthermore, the easy interconversion between the uncommon η³-butadienyl palladium intermediate featuring a weak C=C/Pd coordination bond and a stable Csp²−Pd bond is beneficial for the dynamic kinetic asymmetric transformation process (DyKAT).     

Stereospecific Photoredox-Catalyzed Vinylations to Functionalized Alkenes and C-Glycosides**

We report an efficient radical-mediated C−C coupling through photoredox-catalyzed reactions of 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO). This transition-metal-free and mild photocatalytic method has excellent functional group tolerance and affords vinylated products in good yields, with complete retention of the alkene configuration. The utility of the methodology is demonstrated by the diastereoselective synthesis of C-vinyl glycosides. Preliminary mechanistic studies suggest that the C−C bond formation is stereospecific and proceeds through a concerted radical coupling transition state.     

Stereoselective Assembly of Hydrogen-Bonded Anionic Cages Dictated by Organophosphate-Based Chiral Nodes

Inspired by the signal transduction function of organophosphates in biological systems, bioactive organophosphates were utilized for the first time as chiral nodes to dictate the stereoselective assembly of hydrogen-bonded anionic cages. Phosphonomycin (antibiotics), tenofovir (antivirals), adenosine monophosphate (natural product, AMP) and clindamycin phosphate (antibiotics) were assembled with an achiral bis-monourea ligand, thereby leading to the stereoselective formation of quadruple or triple helicates. The extent of the stereoselectivity could be enhanced by either lowering the temperature or adding stronger-binding cations as templates. With the chiral anionic cages as the host, some enantioselectivity was achieved when binding chiral quaternary ammonium cations.     

Diazoalkenes: From an Elusive Intermediate to a Stable Substance Class in Organic Chemistry

Over decades diazoalkenes (R₂C=C=N₂) were postulated as reactive intermediates in organic chemistry even though their direct spectroscopic detection proved very challenging. In the 1970/80ies several groups probed their existence mainly indirectly by trapping experiments or directly by matrix-isolation studies. In 2021, our group and the Severin group reported independently the synthesis and characterization of the first room-temperature stable diazoalkenes, which initiated a rapidly expanding research field. Up to now four different classes of N-heterocyclic substituted room-temperature stable diazoalkenes have been reported. Their properties and unique reactivity, such as N₂/CO exchange or utilization as vinylidene precursors in organic and transition metal chemistry are presented. This review summarizes the early discoveries of diazoalkenes from their initial postulation as transient, elusive species up to the recent findings of the room-temperature stable derivatives.